This project will continue investigation on the elucidation of the metabolic pathway of neutral sterols to bile acids, especially regarding: a) the pathway from cholestanol to allo bile acids, b) the details of 12alpha-hydroxyplation of the sterol nucleus as related to the productionof 5alpha- and 5Beta-bile acids, and c) improved methods of separation and quantitation of conjugated and free bile acids by HPLC, and improvement of a computerized data acquisition system for mass spectrometric identification of bile acids and their derivatives.